From Dr. Roy Spencer’s Global Warming Blog
2026 by Roy W. Spencer, Ph. D.
NOTE: I’ve made a couple of updates/clarifications below based upon comments on this post.
Lake Mead behind Hoover Dam is now within several feet of the lowest level at which turbine power generation must be greatly curtailed. Recent news articles often blame the cause on a “millennium drought” being experienced in the West. Of course, much of the western U.S. experiences drought conditions every summer, which is part of the normal climate there. Tens of millions of people like to live where it is sunny most of the year, and agriculture thrives where photosynthesis (lots of sunshine) is abundant… assuming enough water supply for irrigation.
Obviously, people need water, which is why virtually no one lives in the Sahara Desert. Add in the beauty of the Pacific Ocean, and it was inevitable that water demand would exceed supply. Even in 1922, before most people moved out west, the Colorado River Compact was negotiated to divide up the Colorado River’s water among seven southwestern states: California, Nevada, New Mexico, Arizona, Colorado, Utah, and Wyoming.
Most of the water in the Colorado River is from snowmelt in the Rocky Mountains. Most (50% to 70%) goes to agriculture. And, yes, the annual runoff flows into Lake Mead (which was filled after construction of Hoover Dam was mostly completed in 1935) have been below “normal” in recent years. But calling recent reduced streamflow (and as a result, lower Lake Mead water levels) the result of a “millennium drought” is sloppy reporting.
Numerous studies suggest that the original Colorado River Compact of 1922 was based upon a period of unusually high precipitation. This was discussed in a paper entitled “New Streamflow Reconstructions for the Upper Colorado River Basin: Placing Recent Droughts into a Centuries-Long Context“, which is a very readable review of various studies that have reconstructed Colorado River flows at Lee Ferry over the last 500 years from tree ring data. While the paper is a little dated (2006), the conclusions remain the same today.
Here are a couple of noteworthy quotes from that paper (bold added):
“The Stockton and Jacoby reconstruction of the annual flows from 1520 to 1961 contained several important findings, including that the highest sustained flows in the entire record occurred in the first part of the 20th century, the period upon which the Colorado River Compact of 1922 was negotiated, while the most persistent and severe drought occurred in the late 16th century.“
“…Colorado River allocations were based on one of the wettest periods in the past five centuries, while droughts more severe than any 20th-21st century event have occurred in the past.”
I’ve created a chart of the annual streamflows at Lee Ferry with some annotations showing periods of 3+ year droughts, the long-term trend (5th order polynomial fit) since stream gage data started in 1906, and four different estimates of the long-term (500-year) normal streamflow at Lee Ferry reconstructed from tree ring data.(UPDATE: the 2026 estimate is not just a repeat of the 2025 measurement, it is the central estimate of several quantitative evaluations of what the 2026 water year [October through September] will be based upon Lee Ferry gage measurements.)
As can be seen, the period before Hoover Dam was constructed was unusually wet. From the 1930s onward, there has been little net trend with some very wet years and very dry years, with up to a factor of 4-to-5 variations in the annual flows into Lake Mead. Six drought periods of at least 3 consecutive years are shown in red. Note that it took only 5 years to completely fill Lake Mead, which was accomplished by reducing the streamflow below the dam by about 30% to 40% of what the normal flows have been in recent decades.
From the above graph, I think one would be hard pressed to say there has been a statistically significant decrease in streamflow since the 1930s. (UPDATE: the linear trend for 1932 [a wet year] to 2025 is -0.013 +/- 0.016 million acre-feet per year, so it is not significant at the 68% confidence level). The major problem is that water usage exceeds what Mother Nature can reliably provide on a long-term basis. Several years ago I discussed this problem in a post in which I included the following graph (also rather dated) of Colorado River water supply versus usage.
As can be seen, since about 2000, usage has exceeded supply, and given the natural multi-year variations in streamflow, it was only a matter of time before Lake Mead water levels would fall to operationally low levels.
In that same post I showed the average of over 100 CMIP6 climate model runs that show precipitation in the Colorado River watershed increasing substantially with global warming, so blaming the recent dry years on human-caused climate change seems a stretch. (UPDATE: While it is true that drought is a function of both precipitation and evaporation, and warming can cause drought even if precipitation does not change, water releases from Hoover Dam have been declining since 1998, so increased evapotranspiration from irrigation uses downstream of the dam [the main use of Colorado River water] cannot explain decreasing Lake Mead water levels. Direct evaporation from the lake surface is very small and changes little with warming. And there has been no statistically significant trend in streamflow input at Lee Ferry since 1932.)
And calling the recent dry years a “millennium drought” is just fake news
Do any of the scare articles of climate change drought mention the fact that FDR CCC depression era spending paid for a tunnel project through the Rocky Mountains to divert western slope water to Eastern slope ranchers? You can see the heavy flow of water running through the town of Estes Park, Colorado. Power politics diverts water and even drills through mountain ranges.
Watch this video and note how the growth in Las Vegas since 1986 has influenced the lake levels behind Hoover Dam
https://www.youtube.com/shorts/kmh4m_RDnH8
And watch how the costs and taxes in California drove growth in Las Vegas, Arizona, and sw Utah.
The population of the Las Vegas valley was estimated at 25 souls in 1900. It now stands at nearly 3 million for the entire valley.
The DESERT Southwest doesn’t have a water problem.
It has a people problem
The supply/demand problem is created on purpose to create an emergency that then can be blamed on climate.
It is well known for decades that several places will eventually run out of water if no new reservoirs and desalination plants are being built to counter the increase in population and the depletion of groundwater.
But even if things are so obvious that even crazy Californians realise it and vote for the building of new reservoirs(the last time this open air asylum showed a sense of reason),
nothing is being done in years.
Instead they destroyed 3 dams and keep on relying on a system that was improved last time in the 70ies when the population was half as big.
That growth sounds like Vegas is heading for a catastrophe but it lacks context. The Vegas region has some of the most innovative water conservation programs in the SW including instrumenting their water supply and monitoring leaks and using zoning laws to restrict water intensive usages.
They have been so successful that:
Compare that to the profligate water usage in desert climates in California like the Desert Palms area and what Las Vegas has accomplished is impressive.
If I remember correctly they even reprocess, and make potable again, around 50% of the wastewater from the area and, by agreement of the other states in the compact, pump the purified water back into Lake Mead for use again without it counting against their own water allocation from the Colorado River.
The astounding population sounds unsustainable over the last 100 years. Throw in the absolutely massive tourism industry, and if you don’t understand their conservation efforts, you would wonder if they can sustain their way of life but.. even with all of that they still only use 62% of their water allocation.
If only California could say the same thing.
Profligately, the answer selection provided should be in the form of:
A) as listed
B) as listed
C) All of the above
D) Neither A) nor B)
Not sure it’s a people problem, as most of the water is for crops not people. Seems like a combination of over use and climate change, both in play.
That would be the climate change for which there is no (planetary) mechanism — only celestial. In other words, the much ballyhooed imaginary change that is dogma for believers.
Who is eating the crops if It’s not a peoples problem?
And can you name at least a single climate zone that has actually changed into a different climate in this world of climate change?
Btw – it is a “peoples problem”.
Wikileaks released some years ago some documents from a PRIVATE intelligence.
Stratfor maybe.
It was about Lybias population and that the countries population is way above its carrying capacity – and that the only reason was Lybias desalination plant and the great water project.(a massive framework of pipelines).
Intelligence agencies don’t use crap like climate change in internal memos,
Obama then bombed those pipelines(100% civilian infrastructure) and Lybia went from richest African country to failed state with slave markets while it previously was the only arab country that hasn’t exterminated its black slave population after they were forced to end slavery.
Why do you think Clinton destroyed Al Shifa in Sudan, which resulted in the increase of child mortality by 1.2 mio in this region.
It’s always about people.
Why do you think the number of Covid victims in the USA was 4 times higher(population adjusted) than in Belarus with no lockdowns and vaccines at all and why the IMF offered Belarus a 950 mio loan if they do lockdowns?
Climate extinction….c’mon you guys remarketed already. It’s not your global warming.
“…water releases from Hoover Dam have been declining since 1998, so increased evapotranspiration from irrigation uses downstream of the dam [the main use of Colorado River water] cannot explain decreasing Lake Mead water levels.”
If most of the water taken from the Colorado for irrigation uses is taken downstream from the dam what is the water in the reservoir and above used for besides generating electricity? The models show that the watershed should receive more precipitation from global warming, has that not happened and how much precipitation has the watershed received?
The overpaid climate experts at UC Boulder are too busy hiking and rock climbing to answer that one. I’m sure Climate AI can come up with a clever workaround.
Stream flows at Lee’s Ferry are regulated by another dam about 14 miles upstream at Glen Canyon, which impounds yet another reservoir, Lake Powell. In addition, the Colorado River is not the only substantial drainage system that feeds these reservoirs. The Green River also supplies water to them, making confluence above Cataract Canyon.
There is substantial agriculture involved along the way. The Lake Mead situation is therefore a bit more complex than is addressed in Dr. Spencer’s article.
Another note of interest: in 1983 inflows to Lake Powell were so extreme that the lake almost overtopped the dam, which would have been disastrous. As I understand it, they had to hastily purchase plywood at Home Depot to bolt to the top of the dam to prevent an overflow. The variability of the drainage system is remarkable.
I was on Lake Powell in a friend’s boat in the 1990s. The bathtub ring was more than 50 feet above lake level. Today the water level has dropped significantly. The reason is the same that Dr. Spencer has describe for Lake Meade – too much withdrawal.
“But calling recent reduced streamflow (and as a result, lower Lake Mead water levels) the result of a “millennium drought” is sloppy reporting.”
You still don’t get it. It’s not “sloppy”, it’s the agenda.
Place a surcharge of 10 cents/kWh on electricity sent to Nevada and Las Vegas and others will quickly reduce consumption, which means the reservoir will fill up.
Any data and AI centers, etc, which guzzle a lot of electricity must have their own 60%-efficient, gas-fired, combined-cycle gas turbine plants, that must have enough MW capacity, so 30% of output is fed to the HV grid at all times, with the rest powering Owner’s facility.
Which power companies are sending electricity to Nevada? Certainly it is not electricity producers in California. We import 25 to 30% of the electricity that we use in California. In spite of this, morons are still pushing to shut down Diablo Canyon. That would shut off 9% of California’s domestic electricity production raising imports to 34 to 39%. The result would be rolling black-outs.
Less going in, more going out.